Process for producing double-oriented magnetic steel sheets



Oct. 19, 1965 KENJI TAKAHASHl 3,212,942

PROCESS FDR PRODUCING DOUBLE-ORIENTED MAGNETIC STEEL SHEETS Filed March 8, 1963 6 Sheets-Sheet l INVENTOR Kenji Takahashi BY miewfiw Mfr 6 W PROCESS FOR PRODUCING DOUBLE-ORIENTED MAGNETIC STEEL SHEETS Filed March 8. 1963 6 Sheets-Sheet 2 PIC-3.3

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INVENTOR Kenji Takahashi wnzwq g z .62! W76 Oct. 19, 1965 KENJI TAKAHASHI PRQCESS FOR PRODUCING DOUBLE-ORIENTED MAGNETIC STEEL SHEETS 6 Sheets-Sheet 3 Filed March 8, 1965 Oct. 19, 1965 KENJI TAKAHASH! PROCESS FOR PRODUCING DOUBLE-ORIENTED MAGNETIC STEEL SHEETS 6 Sheets-Sheet 4 Filed March 8. 1963 m o a 2. i xv 7 FIG. 7

m M ma VM m n e K Oct. 19,

1965 KENJI TAKAHASHI 3,212,942

PROCESS FOR PRODUCING DOUBLE-ORIENTED MAGNETIC STEEL SHEETS Filed March 8, 1963 Magnetic torque in dyne/cm 6 Sheets-Sheet 5 Oct. 19, 1965 KENJI TAKAHASHI PROCESS FOR PRODUCING DOUBLE-ORIENTED MAGNETIC STEEL SHEETS Filed March 8, 1963 6 Sheets-Sheet 6 m m h H H 1 L L LC C C 6 Z G 6 26 2 Z O 5 7 4% O O T OQ I! .2 m 8 m M OIL m 8 6 4 2 0 $326 5 m c2339: Q2232 Mognefizing force H in Ge IN VE N TOR Kenji Takahashi United States Patent 3,212,942 PROCESS FOR PRODUCING DOUBLE-ORIENTED MAGNETIC STEEL SHEETS Keuji Takahaslli, Tsukita, Yawata, Fukuoka Prefecture, Japan, assignor to Yawata Iron & Steel Co., Ltd., Tokyo, Japan, a Japanese corporation Filed Mar. 8, 1963, Ser. No. 263,940 Claims priority, application Japan, Mar. 19, 1962, 37/ 10,833 1 Claim. (Cl. 148-112) This invention relates to a process for producing double-oriented magnetic steel sheets by a simple and easy method by using a single-oriented magnetic steel sheet as a starting material.

As is well known, among magnetic materials, silicon steel sheets are very important materials for consrtucting electric machines and apparatuses and are used in such great quantities that remarkable progress has been made in studies and in production thereof.

Anisotropic steel sheets are those, which are prepared by arranging the easy magnetization axis of the crystal grains in a specific direction and noticing the magnetic anisotropy of the crystal grains forming them. The tremendous research done on single-oriented silicon steel sheets have been nothing but efforts to orientate the [100] direction of the easiest magnetization axis of the silicon iron crystal grains in the rolling direction and the (110) plane of the crystals in parallel with the rolling plane with respect to their compositions, blooming conditions, rolling conditions, annealing conditions and the combination of these. This grain texture is of the (110) [001] or cube on-edge type, namely the grains have a single orientation. As results of these efforts, silicon steel sheets which have superior magnetic properties in the rolling direction can be produced today, however, as most crystal grain of such steel sheets are so arranged that the [011] direction of the more difiicult magnetization axis orientate themselves in the transverse direction to the rolling direction, the magnetic properties in the transverse direction are far inferior than in the rolling direction. Therefore, the application of single-orientated silicon steel sheets has been limited. Sheets of this kind are used exclusively as spiral or wound cores or frameshaped iron cores specially arranged. Double-oriented magnetic steel sheets are those, in which such disadvantages have been eliminated by arranging the cube edge of the grains so that they are parallel to the sheet edge or the direction of rolling and in a transverse direction in the plane of the sheets. This grain texture is of the (100) [001] or cube on face type, namely the grains have a double orientation. That is to say, the doubleoriented magnetic steel sheet having such cubic texture has also, in the transverse direction, the same excellent magnetic properties as in the rolling direction of a singleoriented magnetic steel sheet having a (110) [001] grain texture or a Goss texture.

The heretofore disclosed methods of producing doubleoriented silicon steel sheets seem to be classified substantially into the following three categories. The first is a method wherein a hot-rolled sheet is successively rolled in two directions at right angles with each other. This method was suggested long ago. As is well known, this cross-wise rolling method or the like diagonal rolling method wherein the material is cold-rolled at an angle of 50-70 degrees to the rolling direction requires much time and a high degree of experience and technique. Therefore, not only is it not easy to practice such a method but also special techniques are required in order to apply this method to steel strips. The second is a method which was first initiated, in the USA. and then improved in Japan, wherein, on the basis of the known experimental fact that the crystal orientation of ice columnar crystals of the ingot has the [100] axes on their growing direction, an ingot with crystal orientation is made by a special technique and then a double-oriented silicon steel sheet is produced by a strictly controlled proper rolling and recrystallizing heat-treatment. However, the production of the oriented ingot and rolling thereof must be technically subjected to various limitations. The third is a method of obtaining cubic textures by carrying out cold-reducing of more than 50% or, more specifically, strong cold-reducing of more than as the main process and, carrying out purification in the final annealing for the secondary recrystallization, specifically, by keeping the oxygen partial pressure on the surface of the material as low as possible by using a getter or a catalyst or controlling the surface energy condition to a certain extent so that the second recrystallization may fully take place. The simplest is a method wherein a magnetic material having a Goss texture is used as a starting material. When a thin silicon steel plate having the Goss texture is cold reduced by more than 60%, its main cold-rolled grain texture will become the (111) [112 type (see FIGURE 6) and then the secondary recrystallization is fully developed at a temperature of ll00l400 C.

The first important condition which is common to all of those methods is the strong cold-rolling at a reduction of more than about 60% in thickness and the second important condition is the specifically considered annealing condition. However, in reexamining the first necessary cold-rolling condition, it is found to have a disadvantage which can be said to be fatal for the industry, especially in the method wherein a material having the Goss texture is used as a starting material. That is to say, a single-oriented silicon steel sheet 1.0 mm. thick is required as the starting material, if the necessary coldreducing is made, for instance, 70% in order to produce a double-oriented silicon steel sheet 0.3 mm. thick. If a thicker double-oriented silicon steel sheet should be produced, and a stronger cold-rolling is to be applied as a necessary condition, a method of preparing single-oriented silicon sheets several millimeters thick will have to be established in advance. The cold-rolling of a silicon steel sheet of such thickness may not be said to be technically impossible but will be practically nearly impossible because of the rolling equipment. Particularly, in the case of a steel strip, it will be subjected to further limitations in respect to thickness and it will be very difficult to produce the required Goss texture in the steel strip of such thickness. Therefore, the application of those methods including that of Vacuum Schmelze A.G. will be practically limited only to very thin sheets in the industry.

In contrast to the above mentioned conventional methods, the present invention has established a new method of producing double-oriented magnetic steel sheets wherein the defect of the conventional methods has been eliminated and which is characterized by using a singleoriented magnetic steel sheet as a starting material as in the conventional method, but the fundamental idea of the conventional methods of applying a strong coldrolling has been replaced by utilizing skillfully the property of the crystal surface energy and applying a proper weak cold-rolling and recrystallizing annealing so that a cubic texture may be produced.

An object of the present invention is to provide a process for producing double-oriented magnetic steel sheets which is easily applicable even to thicker steel sheet products.

Many other objects and advantages of the present invention will become apparent from the following description.

An embodiment of the present invention shall be described in the following with reference to the accompanying drawings.

In the drawings,

FIGURE 1 is a (110) pole figure of a single-oriented silicon steel sheet (of a Goss texture);

FIGURES 2 to 6 are pole figures of the (110) planes of the crystals of steel sheets having the Goss texture as cold-rolled at reduction of 20%, 28%, 33%, 38% and 67 respectively;

FIGURE 7 is a pole figure of the (110) plane of the crystals after the intermediate annealing according to the present process;

FIGURE 8 is a pole figure of the (110) plane of the crystals of a double-oriented silicon steel sheet produced by the present process, all being prepared with X-rays;

FIGURE 9 is a curve diagram comparatively showing magnetic torque curves of a double-oriented silicon steel sheet produced by the present invention and a commercial single-oriented silicon steel sheet;

FIGURE 10 shows magnetization curves of a doubleoriented silicon steel sheet produced by the present invention and a commercial single-oriented silicon steel sheet.

The process of the present invention shall now be described in detail. As a starting material, there was used a single-oriented silicon steel sheet consisting of crystals having the [001] axis of the crystal in the rolling direction and the (110) plane of the crystal in parallel with the rolling plane. That is to say, the starting material in the present invention is shown as the (110) plane pole figure is as in FIGURE 1.

In the figure, RD denotes the rolling direction and TD denotes the transverse direction to the rolling.

Said figure is of a typical Goss texture wherein the degree of concentration of the pole is very high and it is seen from the magnetizing torque curves (see FIG- URE 9) and others that more than about 80% of the crystals have the (110) [001] orientation.

The (110) plane pole figure was prepared with X-rays by using MoK, rays.

When using the above mentioned single-oriented silicon steel sheet, the composition forming the steel is not a specific problem and the thickness also need not be specifically limited. Needless to say, it is possible to utilize any general commercial single-oriented silicon steel sheet. Also a single-oriented magnetic steel sheet containing Al and others can be used as a starting material. When an insulating coating or the like has been applied to the surface of the steel sheet starting material, the coating should be removed at the start by being pickled for about 10 minutes in an acid such as, for example, 30% hydrochloric acid kept at 80 C.

Then, the steel sheet is dried and is then cold-rolled at a reduction of 20 to 50% at room temperature in the [100] direction. The number of passes in such case are not specifically limited. However, it is economically disadvantageous to increase the number of passes. Therefore, there should be less than passes. The reasons for having cold-rolling reduction to 50% in the present invention are that generally weak cold-rolling is technically easier and economically more advantageous than strong cold-rolling in various points, but more concretely, when applying a reduction of more than 50%, a very thick single-oriented magnetic steel sheet will be required as a starting material, particularly when desiring a thicker product. But, this is very difficult, technically, to achieve. So, if a single-oriented magnetic steel sheet of an industrially feasible thickness is used as a starting material, only a thin product must, of course, be expected. Then, if the reduction is less than 20%, no double-oriented texture will be produced.

The (110) plane pole figures of steel sheets at rolling rates in this range are as shown in FIGURES 2 to 5. In FIGURE 2, as evident in comparison with FIGURE 1, with the cold-rolling reduction of about 20%, the texture keeps substantially the original type and is the (ll0)[00l] type. The (110) plane pole figure of the steel sheet cold-rolled at an increased rolling reduction of 28% is as in FIGURE 3. This is made by overlapping three (llO) plane pole figures prepared by sweeping the surface of the samples about 30 mm. with X-rays substantially on the whole angle. (In the figure, the mark represents the (110) plane pole of the (ll0)[00l] single crystal.) The (110) plane pole has begun to deviate a little from the ideal (ll0)[00l] position but the main orientation is still expressed as (110) [001] type. FIGURE 4 is made as in the preceding figure by overlapping three (110) plane pole figures of steel sheets as reduced by 33% by further increasing cold-rolling. The deviation of the (110) plane pole increase a little but, judging from its state of distribution, it may be considered to be still of a deviated dispersed (ll0)[00l] type texture. When the reduction of the cold-rolling is further increased to 38%, the tendency of forming a new structure appears as shown in FIGURE 5. This represents the state before shifting to the (lll)[ll] type texture. The (lll)[11'2 type cold-rolled texture is produced by cold-reducing the (ll0)[00l] type texture or the Goss texture by more than 50%. Its typical (110) plane pole figure is as shown in FIGURE 6 which is a 67% cold-rolled texture. Such typical (1l1)[ll2] grain texture is hardly produced below a rolling reduction of about 50%.

The above mentioned method is to utilize the (l1l)[ll] type texture produced inevitably by coldreducing by more than 60%.

The present invention effects cold-reducing by 20 to 50% in thickness as described above. Therefore, the cold-rolled texture of the steel material is a somewhat dispersed and transformed form of the (110) [001] type texture. That is to say, the present invention utilizes the deformed (110) [001] texture produced by the coldrolling reduction of more than 20% but less than 50% or preferably from about 25% to about 45%.

The thus cold-rolled steel sheet is then intermediately annealed. The intermediate annealing is carried out for a time adapted to substantially complete the recrystallization or preferably for more than about 20 hours but less than about 40 hours at a temperature of 1000 to 1200 C. The atmosphere for such intermediate annealing need not have any specific conditions. But hydrogen or an inert atmosphere of high purity that has been heretofore recommended as the annealing atmosphere for high grade silicon steel sheets is required. It is sufficient that the dew point is below --40 C. and the oxygen content is less than about p.p.m. An N -atmosphere is not recommended in the case of a magnetic Fe-Al material, because this is likely to produce detrimental AlN in the steel sheet. When annealing in a vacuum, the vacuum should be made less than 10- mm. Hg. In such annealing, a layer of such inorganic refractory material as A1 0 or MgO should be inserted between the laminated steel sheets or coiled steel strips for the purpose of preventing the sheets from sticking together. For that purpose, a powder of 10 30a may be applied as sieved or a mixture thereof with water, may be applied. However, any inorganic refractory material as pure as possible should be selected. It is preferable that the cooling rate of the steel sheet is less than 50 C./ hr. As in the later described example, the plane pole figure after the intermediate annealing will be as shown in FIGURE 7, presenting no property of double-orientation.

The above mentioned intermediately annealed steel sheet is then subjected to skin pass-rolling as the next step. Such skin pass-rolling is carried out at a rolling reduction of 0.5-2.5 at room temperature. If the rolling reduction is below 0.5%, the stress energy, which will be a driving force in the recrystallization, will not be sufiicient. If

5 it is above 2.5%, no favorable cubic texture will be formed. The proper number of rolling passes is less than 10.

Lastly the sheet is finish-annealed. The finish-annealing conditions are selected as follows. That is to say,

6 maximum magnetic induction Bm is 10,000 and 15,000 G, respectively.

(2) B B B and B represent magnetic inductions when the magnetizing force is 1, 3, 10 and 25 Oe., respectively.

(1) H and H represent coercive forces when the the annealing is carried out at a temperature of 1150 to 5 (3) W. /50 and w. /50 represent core losses at 50 1250 C. for a time sufficient to finish the secondary c./s. when Bm is 10,000 and 15,000 G, respectively. recrystallization or preferably between about to 40 (4) The direction of the sample tested is the rolling hours. By such steps, such excellent cubic texture (see direction (L direction).

FIGURE 8) as is seen in the later mentioned example 10 (5) M and L is the first and the second maximum of can be formed. The annealing atmosphere for the finishthe magnetic torque curve.

annealing may be an atmosphere of such high purity as is As is evident, the magnetic characteristics were excelsuflicient for the secondary recrystallization to take place. lent, the total core loss w. 15/50 was 0.95 w./kg., the max- It need not have any specific strict conditions but may be imum magnetic torque was so high and the ratio M/L was considered to be the same as the intermediate annealing 15 1.09 that the cubic texture was also excellent. atmosphere. In the case of this annealing, as in the inter- EXAMPLE 2 mediate annealing, the sticking together of the steel sheets is prevented by an inorganic refractory material. The The Same commercial Single-Oriented silicon Steel cooling rate of the steel sheets should be such as will not sheets (Z11) 0.30 mm. thick as in Example 1 were used as .give any undesirable internal change, for example, strain 20 starting materials.

and is preferably less than 50 C./hr. These steel sheets were pickled in an aqueous solution Examples of the present invention shall be explained in Of 30% hy ro hl r d at fOr 10 minutes, were the following: then cold-rolled at rolling reductions of 24, 30 and 38%,

EXAMPLE 1 respectively, with 10 to 15 passes, were subsequently in- Table 1 Alternating current Direct current magnetic characteristics (50 c./s.) magnetic Orientation characteristics Sample No. Maximum Coercive force Magnetic induction in gansses magnetic Core loss in w./kg. Magnetic torque in in Oe. permea- X104 dyne/cm.

bility H6 H6 B1 B5 B10 B in W. 10/50 I W. 15/50 M L M/L E848 0.060 0.070 15,900 16,750 17, 600 18,900 65,000 0. 44 i 0. 95 17.7 16.2 i 1. 09

A commercial single-oriented silicon steel sheet (Yawata termediately annealed in an N atmosphere of a dew point 'OrientCore Z11 corresponding to Armco Oriented M- of 46 at 1200 C. for 20 hours and were cooled at 6W) 0.30 mm. thick was used as a starting material. 50 C./ hr.

This steel sheet was pickled in an aqueous solution of The texture of the material after intermediate annealing hydrochloric acid at 80 C. for 10 minutes, was then 45 of the 30% cold reduced sheets are shown in FIGURE 7. cold-rolled at a rolling reduction of 30% with 10 to 15 As shown in FIGURE 7, at this stage, the cubic texture .passes, was subsequently intermediately annealed in a has not appeared in any way, in this example. H I vacuum of less than 10- mm. Hg at 1150" C. for 40 The sheets were then skin pass-rolled at rolling reduchours, was cooled at 50 C./,hr., was then skin pass-rolled tions of 1.0 and 1.5% with 6 to 10 passes to get sufficient at a rolling reduction of 1.0% with 6 to 10 passes, was 50 stress energy, were then finish-annealed in an N atmos- 'finally finishannealed in a vacuum of less than 10' mm. phere of a dew point of C. at 1200 C. for 20 Hg at 1200 C. for 40 hours and Was cooled at C./l1r. hours and were cooled at 50 C./hr. The results of the The magnetic characteristics of the thus obtained doublethus obtained double-oriented silicon steel sheets are shown K oriented silicon steel sheet are shown in Table 1. in Table 2. The data are only of the rolling direction.

Table.2

Alternating Direct current magnetic characteristics current (50 c./s.) Orientation magnetic characteristics Oold- Skin Sample No. rolling pass in Maximum Maximum magnetic in percent percent Coercive force Magnetic induction in gausses magnetic Core loss in w./kg. torque in X104 dyne/ in Ca. permeacm.

bility 11, H. B; B3 B16 B25 p.111 W. 10/50 W. 15/50 M L M/L GES4 1- 24 1.0 0. 094 0.105 16,000 17,000 17,750 18,750 48,000 0.77 1.71 17.3 16.0 1.02

GES8- 38 1.0 0.069 0.083 16,000 16,550 17,350 18,250 73,800 0.62 1.16 16.7 15.5 1.08

Remarks: As seen in this table, the ratio M/L of the successive maximum magnetic torque M and L is 1.02-4.08 and 7 shows a remarkable double-orientation. FIGURE 8 shows a pole figure obtained when several samples selected from the double-oriented silicon steel sheets obtained by the method of the present invention as shown in this and the other two examples were analyzed with X-rays and the thus obtained (110) plane pole figures were overlapped. As seen in said figure, the texture of the product is shown to be a favorable cubic texture, the (100) planes of the crystals substantially parallel to a rolling plane with a deviation of only several degrees and the [001] directions of the crystals have a spread of above 15 degrees on the right and left. The mark [I] in the figure denotes the (110) plane pole of the (100) 1] single crystal.

EXAMPLE 3 The same commercial single-oriented silicon steel sheets (Z11) 0.30 mm. thick as in Example 1 were used as starting materials.

These steel sheets were pickled in an aqueous solution of 30% hydrochloric acid at 80 C. for minutes, were cold-rolled at a reduction of 30% with 10 to 15 passes, were subsequently interme-diately annealed in an Ar atmosphere of a dew point of 47 C. at 1000 C. for hours, were cooled at 50 C./hr., were skin pass-rolled at a reduction of 1.0% with 6 to 10 passes, were finishedannea-led in an Ar atmosphere of a dew point of 47 C. at 1200 C. for 40 hours and were cooled at 50 C./hr. The results of the thus obtained double-oriented silicon steel sheets are shown in Table 3. In the table, L represents the sample in the rolling direction and C represents the sample in the direction at right angles to the rolling.

As evident from the above figure, in comparison with the magnetization characteristics of so-called Goss steel sheet which shows the excellent magnetization only in the rolling direction, the double-oriented steel sheet obtained by the method according to the present invention shows the following advantage:

That is to say, in the rolling direction L the magnetization characteristics (shown with the curve GL) of the steel sheet obtained by the present invention are so excellent as or even somewhat better than those (shown with the curve ZL) of the Goss steel sheet, and in the transverse direction C the magnetization characteristics GC of the former are so far improved that they are nearly equal to those of the latter in the rolling direction. Thus, in the double-oriented steel sheet obtained by the present invention such excellent magnetization characteristics as in the rolling direction of the'Goss steel sheet are found not only in the rolling direction but also in the direction transverse to the rolling direction.

What is claimed is:

A method for producing double-oriented magnetic steel sheet having grain texture of (100) [001] orientation from single-oriented magnetic steel sheet having grain texture of (110) [001] orientation, comprising the steps of (1) pickling single-oriented magnetic steel sheet having grain texture of (110) [001] orientation,

(2) cold-rolling said sheet at a reduction rate of 20 to with 10 to 15 rolling passes, whereby the grain texture of deviated dispersed (110) [001] orientation is maintained in said sheet,

Table 3 Alternating Direct current magnetic characteristics current c./s.) Orientation magnetic characteristics Sample Direction Cold- Skin N0. of rollingin pass in Maximum Maximum magnetic sample percent percent Coercive force Magnetic induction in gausses magnetic Core loss in w./kg. torque in X10 dyne/ in e. permeaem.

bility H0 IL 131 B3 131 13 ,im W. 10/50 W. 15/50 M L M/L GES49 L 38 1.0 0.072 0.093 15,500 16,750 17,850 18,750 51,300 0.57 1. 04 17.5 16.9 1.03

GES49. C 38 1.0 0.078 0.101 15,000 16,300 17,000 17,700 48, 700 0.52 1.03 17.4 17.1 1.02

In this case, there were obtained remarkable doubleoriented silicon steel sheets in which the magnetization characteristics were a little worse, the maximum magnetic permeability was about 50,000 and very excellent in the rolling direction and was about 50,000 in the transverse direction, too, the maximum magnetic torque value was more than 17 10 dyne/cm. and the ratio of the successive maximum magnetic torque values was shown to be about 1.02.

FIGURE 9 shows the magnetic torque curve of the sample No. GES49 in Table 3 as compared with that of the single-oriented silicon steel sheet (Z11) which is the starting material. Both represent typical excellent cubic texture and Goss texture, respectively. That is to say, in the sample GES49, M=17.1 and 17.7, averaging 17.4, L=16.5 and 17.6, averaging 17.1 and M/L=1.02 :and, in the sample Z11, M=l5.8 and 16.5, averaging 16.2, L=5.7 and 6.1, averaging 5.9 and M/L=2.75.

FIGURE 10 shows the magnetization curves G of the L direction sample and the C direction sample shown in Table 3 as compared with the magnetization curves Z of the L and C direction samples of the starting material. HI and Hh in the figure correspond to the upper scale HI n the under cale Hb in the abscisa, respectively.

(3) intermediately annealing said cold-rolled sheet at temperature of from 1000 to 1200 C. in a nonoxidizing atmosphere for 20 to 40 hours,

(4) cooling said annealed sheet to room temperature at a cooling rate below 50 C./'hr.,

(5) cold-rolling said cooled sheet at a reduction rate of 0.5 to 2.5% with 6 to 10 rolling passes to obtain the final gauge,

(6) finally annealing the thus cold-rolled sheet at a temperature of from 1150 to 1250 C. in a nonoxidizing atmosphere for 20 to 40 hours, and

(7) cooling the thus annealed sheet to room temperature at a cooling rate of below 50 C./hr.

References Cited by the Examiner UNITED STATES PATENTS 2,076,383 4/37 Pawlek et al. 148--l 11 3,058,857 10/62 Pavlovic et al. 148'l20 3,078,198 2/63 Wiener 148-111 3,089,795 5/63 Hu 14 8l 11 3,090,711 5/63 Kohler 148111 3,105,782 10/63 Walter 148113 3,130,092 4/64 Kohler et al. 1481 11 DAVID L. RECK, Primary Examiner. 

